Abstract
Water is essential for metabolism and all life processes. Despite this, a number of organisms distributed across the kingdoms of life can survive near-complete desiccation or anhydrobiosis (life without water). Increases in intracellular viscosity, leading to the formation of a vitrified (glassy) state is necessary, but not sufficient, for conferring desiccation tolerance. What properties of a vitrified system make it desiccation-tolerant or -sensitive are unknown. We have analyzed 18 different in vitro vitrified systems, composed of one of three protective disaccharides (trehalose, sucrose, or maltose) and varying amounts of glycerol, quantifying their protective capacity and their material properties in a dry state. We find that protection conferred by mixtures containing maltose correlates strongly with increased water content, increased glass-transition temperature, and reduced glass former fragility, while the protection of glasses formed with sucrose correlates with increased glass transition temperature and the protection conferred by trehalose glasses correlates with reduced glass former fragility. Thus, in vitro different vitrified sugars confer protection through distinct material properties. Extending on this, we have examined the material properties of a dry desiccation tolerant and intolerant life stage from four different organisms. In all cases, the dried desiccation tolerant life stage of an organism had an increased glass transition temperature relative to its dried desiccation intolerant life stage, and this trend is seen in three of four organisms when considering reduced glass fragility. These results suggest that while drying of different protective sugars in vitro results in vitrified systems with distinct material properties that correlate with their protective capacity, in nature organismal desiccation tolerance relies on a combination of these properties. This study advances our understanding of how protective and non-protective glasses differ in terms of material properties that promote anhydrobiosis. This knowledge presents avenues to develop novel stabilization technologies for pharmaceuticals that currently rely on the cold-chain.
Statement of significance For the past three decades the anhydrobiosis field has lived with a paradox, while vitrification is necessary for desiccation tolerance it is not sufficient. Understanding what property(s) distinguishes a desiccation tolerant from an intolerant vitrified system and how anhydrobiotic organisms survive drying is one of the enduring mysteries of organismal physiology. Here we show in vitro the protective capacity of different vitrifying sugars can be correlated with distinct material properties. However, in vivo, diverse desiccation tolerant organisms appear to combine these material properties to promote their survival in a dry state.
Highlights
The protective capacities of different glass forming sugars correlate with distinct material properties.
Material properties of dried anhydrobiotic organisms differ dramatically when examined in desiccation tolerant and intolerant life stages.
Organismal desiccation tolerance appears to rely on a combination of properties of the vitrified state including increased glass transition temperature and reduced glass former fragility.
Competing Interest Statement
The authors have declared no competing interest.
